Solution:
The complete figure of question is attached below
From figure,
Write all elements from set A
A = {3, 6, 9, 12}
Write all elements from set B
B = {2, 4, 6, 8, 10, 12}
AUB means A union B
AUB means set of all the numbers combined with set A and set B
Combine set A and B
AUB = { 2, 3, 4, 6, 8, 9, 10, 12}
Thus AUB is found